The ventilation of your hydroponic grow room has two critical factors: the removal of hot air (depleted in CO²) and the entry of new fresh air. Air movement provided by fans such as revolution silence ec fans, facilitate the 0²/CO² exchange of stomata (= gain of liveliness) and expand plant structure (= production gain). Hot air is exhausted using an air extractor and the fresh air can either be provided by a passive ventilation (open window) or through the installation of an Air Conditioning unit, which can also be used as an extractor.
In addition to the control over the temperature, the use of fans allows a control of humidity (or hygrometry). Expressed as a percentage, the quantity of water available in the air is measured with a hygrometer. In most cases, a hydroponic grow tent housing plants in vegetative phase (growth) requires the establishment of a humidifier (cold steam and already equipped with a hygrostat preferably). To maintain the necessary 50 to 70% hygrometry; 45 to 50% relative humidity is sufficient for flowering, to avoid any mould. These measurements ensure optimal gas exchange at the stoma level.
The following method is well known and has been approved by many growers:
NOTE: For the majority of indoor gardens without air conditioning or CO², the rule of thumb is 1 per minute. In this case, multiply the volume of culture by 60 to calculate the volume of air to be renewed per hour.
Finally, when a charcoal filter is attached to the fan, it is expected to decrease efficiency by 25%. This data is variable and depends on the age of the filter, the length and the circulating power of the ducts used between the fan and the filter and other factors. To evaluate this decrease in efficiency by 25, simply multiply by 1.25.
If we record the equation to our grow tent example this equates to:
= 540 m³/h
The end result is the minimum extraction size needed.
Airflow: 540 m³/h
If the growing chamber is in a very well insulated area like a basement, then using that number should be fine. On the other hand, if the growing chamber is located in a location that is very exposed to heat and natural sunlight, such as an upstairs room or an attic, then the size of the extractor needed should be increased by approximately 25%.
By knowing the size of the room and the number of lamps that will be used, you can work on the required ventilation in m3 per hour (m³/h)
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